If the vectors 2i + 4j - 3k, -i + 2j + 3k, and pi - 2j + k are coplanar, then the unit vector in the direction of the vector 9pi - 4j + 4k is:

If a = (0, -1, 2), b = (1, 0, -1) and c = (2, -1, 0), then which of the following is a unit vector parallel to a - b - c?

If a = 2î + 3ȷ and b = î - ȷ, then a - b is:

If vectors a and b are perpendicular with |a| = 5 and |b| = 12, then |a + b| is equal to: